U.S. patent application number 12/716452 was filed with the patent office on 2010-09-09 for n-way divider/combiner, with n different from a power of two, obtained in planar, monolithic, and single-face technology for distribution networks for avionic radars with electronic beam-scanning antenna.
This patent application is currently assigned to Selex Galileo S.p.A.. Invention is credited to Antonino Mistretta, Antonino Spatola.
Application Number | 20100225417 12/716452 |
Document ID | / |
Family ID | 41100905 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100225417 |
Kind Code |
A1 |
Mistretta; Antonino ; et
al. |
September 9, 2010 |
N-Way Divider/Combiner, With N Different From A Power Of Two,
Obtained In Planar, Monolithic, And Single-Face Technology For
Distribution Networks For Avionic Radars With Electronic
Beam-Scanning Antenna
Abstract
A planar N-way power divider/combiner, wherein N is an integer
different from a power of two, comprising a first port, which is to
be coupled to a first transmission line having a first
characteristic impedance, N second ports, which are to be coupled
each to a corresponding electrical load, and N division/combination
branches, each coupled between the first port and a corresponding
second port and each having a first stage, a second stage, and an
intermediate node between the two stages. All the electrical loads
have one and the same given load impedance. For each pair of
planarly adjacent division/combination branches, a corresponding
first uncoupling resistor is coupled between corresponding
intermediate nodes and a corresponding second uncoupling resistor
is coupled between the corresponding second ports.
Inventors: |
Mistretta; Antonino;
(Palermo, IT) ; Spatola; Antonino; (Palermo,
IT) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA, 101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
Selex Galileo S.p.A.
|
Family ID: |
41100905 |
Appl. No.: |
12/716452 |
Filed: |
March 3, 2010 |
Current U.S.
Class: |
333/128 ; 216/13;
430/312 |
Current CPC
Class: |
H01P 5/16 20130101 |
Class at
Publication: |
333/128 ; 216/13;
430/312 |
International
Class: |
H01P 5/12 20060101
H01P005/12; H01P 11/00 20060101 H01P011/00; G03F 7/20 20060101
G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2009 |
IT |
TO2009A000160 |
Claims
1. A planar N-way power divider/combiner (50, 60), wherein N is an
integer different from a power of two (N.noteq.2.sup.K, wherein
K=1,2,3,4, . . . ), comprising: a first port (P.sub.1) intended to
be coupled to a first transmission line (51, 61) having a first
characteristic impedance (Z.sub.0); N second ports (P.sub.2,
P.sub.3, P.sub.4, P.sub.5, P.sub.6) each intended to be coupled to
a corresponding electrical load (52, 53, 54, 62, 63, 64, 65, 66),
all the electrical loads (52, 53, 54, 62, 63, 64, 65, 66) having
one and the same given load impedance (Z.sub.L); and N
division/combination branches (501, 502, 503, 601, 602, 603, 604,
605) each coupled between the first port (P.sub.1) and a
corresponding second port (P.sub.2, P.sub.3, P.sub.4, P.sub.5,
P.sub.6); the planar N-way power divider/combiner (50, 60) being
configured to: divide a first electrical signal present as input at
the first port (P.sub.1) into N second electrical signals; output
each of the N second electrical signals at a corresponding second
port (P.sub.2, P.sub.3, P.sub.4, P.sub.5, P.sub.6); combine N third
electrical signals each present as input at a corresponding second
port (P.sub.2, P.sub.3, P.sub.4, P.sub.5, P.sub.6) into a fourth
electrical signal; and output said fourth electrical signal at the
first port (P.sub.1); the planar N-way power divider/combiner (50,
60) being characterized in that each of the N division/combination
branches (501, 502, 503, 601, 602, 603, 604, 605) comprises a
corresponding first stage (TL.sub.11, TL.sub.21, TL.sub.31,
TL.sub.41, TL.sub.51), a corresponding second stage (TL.sub.12,
TL.sub.22, TL.sub.32, TL.sub.42, TL.sub.52), and a corresponding
intermediate node (N.sub.1, N.sub.2, N.sub.3, N.sub.4, N.sub.5)
between the corresponding first stage (TL.sub.11, TL.sub.21,
TL.sub.31, TL.sub.41, TL.sub.51) and the corresponding second stage
(TL.sub.12, TL.sub.22, TL.sub.32, TL.sub.42, TL.sub.52); the planar
N-way power divider/combiner (50, 60) being further characterized
by comprising also: for each pair of planarly adjacent
division/combination branches (501, 502, 503, 601, 602, 603, 604,
605), a corresponding first uncoupling resistor (504, 505, 606,
607, 608, 609) coupled between the corresponding intermediate nodes
(N.sub.1, N.sub.2, N.sub.3, N.sub.4, N.sub.5), and a corresponding
second uncoupling resistor (506, 507, 610, 611, 612, 613) coupled
between the corresponding second ports (P.sub.2, P.sub.3, P.sub.4,
P.sub.5, P.sub.6).
2. The planar N-way power divider/combiner of claim 1, wherein the
first electrical signal has a first power and a first frequency
comprised in a given frequency band, and wherein all the second
electrical signals have the first frequency and one and the same
second power which is equal to the first power divided by N; all
the third electrical signals having one and the same third power
and one and the same second frequency comprised in the given
frequency band, the fourth electrical signal having the second
frequency and a fourth power which is equal to N times the third
power; all the first uncoupling resistors (504, 505, 606, 607, 608,
609) having one and the same first electrical resistance (R.sub.1);
all the second uncoupling resistors (506, 507, 610, 611, 612, 613)
having one and the same second electrical resistance (R.sub.2); in
each of the N division/combination branches (501, 502, 503, 601,
602, 603, 604, 605) the corresponding first stage (TL.sub.11,
TL.sub.21, TL.sub.31, TL.sub.41, TL.sub.51) comprising a
corresponding second transmission line coupled between the first
port (P.sub.1) and the corresponding intermediate node (N.sub.1,
N.sub.2, N.sub.3, N.sub.4, N.sub.5); in each of the N
division/combination branches (501, 502, 503, 601, 602, 603, 604,
605) the corresponding second stage (TL.sub.11, TL.sub.22,
TL.sub.32, TL.sub.42, TL.sub.52) comprising a corresponding third
transmission line coupled between the corresponding intermediate
node (N.sub.1, N.sub.2, N.sub.3, N.sub.4, N.sub.5) and the
corresponding second port (P.sub.2, P.sub.3, P.sub.4, P.sub.5,
P.sub.6); all the second transmission lines having one and the same
second characteristic impedance (Z.sub.1) and one and the same
first electrical length; all the third transmission lines having
one and the same third characteristic impedance (Z.sub.2) and one
and the same second electrical length; the first electrical length
being an odd multiple of a quarter of a predefined wavelength
(.lamda.) which corresponds to a middle frequency in the given
frequency band; and the second electrical length being an odd
multiple of a quarter of a predefined wavelength (.lamda.) which
corresponds to a middle frequency in the given frequency band.
3. The planar N-way power divider/combiner of claim 2, wherein the
first electrical length is equal to one quarter or to three
quarters of the predefined wavelength (.lamda.).
4. The planar N-way power divider/combiner of claim 2, wherein the
second electrical length is equal to one quarter or to three
quarters of the predefined wavelength (.lamda.).
5. The planar N-way power divider/combiner according to claim 2,
wherein the first frequency and the second frequency are radio
frequencies.
6. The planar N-way power divider/combiner according to claim 2,
wherein the given frequency band is comprised between 8.5 GHz and
10 GHz.
7. The planar N-way power divider/combiner according to claim 2,
wherein N is equal to three, and wherein the second characteristic
impedance (Z.sub.1) is equal to (3Z.sub.0).sup.3/4*Z.sub.L.sup.1/4,
wherein Z.sub.0 denotes the first characteristic impedance, and
Z.sub.L denotes the given load impedance; the third characteristic
impedance (Z.sub.2) being equal to
(3Z.sub.0).sup.1/4*Z.sub.L.sup.3/4,
8. The planar N-way power divider/combiner of claim 7, wherein the
first electrical resistance (R.sub.1) is equal to
(Z.sub.2.sup.2/Z.sub.L)*0.75, wherein Z.sub.2 denotes the third
characteristic impedance; the second electrical resistance
(R.sub.2) being equal to 4Z.sub.L.
9. The planar N-way power divider/combiner according to claim 2,
wherein N is equal to five, and wherein the second characteristic
impedance (Z.sub.1) is equal to (5Z.sub.0).sup.3/4*Z.sub.L.sup.1/4,
wherein Z.sub.0 denotes the first characteristic impedance, and
wherein Z.sub.L denotes the given load impedance; the third
characteristic impedance (Z.sub.2) being equal to
(5Z.sub.0).sup.1/4*Z.sub.L.sup.3/4.
10. The planar N-way power divider/combiner of claim 9, wherein the
first electrical resistance (R.sub.1) is equal to
(Z.sub.2.sup.2/Z.sub.L)*0.4, wherein Z.sub.2 denotes the third
characteristic impedance; the second electrical resistance
(R.sub.2) being equal to 3Z.sub.L.
11. A method of manufacturing the planar N-way power
divider/combiner according to claim 1, the method comprising:
forming a multilayer structure comprising a conductive layer (71),
a resistive layer (72) underneath the conductive layer (71), and a
dielectric substrate (73) underneath the resistive layer (72);
chemically etching and removing, selectively, first portions of
said conductive layer (71) and first portions of said resistive
layer (72) which are underneath the first portions of said
conductive layer (71) in order to form the N division/combination
branches (501, 502, 503, 601, 602, 603, 604, 605); and chemically
etching and removing, selectively, second portions of said
conductive layer (71) in order to form the first (504, 505, 606,
607, 608, 609) and the second (506, 507, 610, 611, 612, 613)
uncoupling resistors.
12. The method of claim 11, wherein forming a multilayer structure
comprises: electrodepositing the resistive layer (72) on the
conductive layer (71); and laminating the resistive layer (72) and
the conductive layer (71) on the dielectric substrate (73).
13. The method of claim 11, wherein chemically etching and
removing, selectively, first portions of said conductive layer (71)
and first portions of said resistive layer (72) comprises: forming
on the conductive layer (71) a first mask which, selectively,
covers the second and third portions of said conductive layer (71)
and exposes the first portions of said conductive layer (71), the
third portions of said conductive layer (71) defining the N
division/combination branches (501, 502, 503, 601, 602, 603, 604,
605), the second portions of said conductive layer (71) being upon
second portions of said resistive layer (72) defining the first
(504, 505, 606, 607, 608, 609) and the second (506, 507, 610, 611,
612, 613) uncoupling resistors; chemically etching and removing the
first portions of said conductive layer (71) so as to leave exposed
the underneath first portions of said resistive layer (72);
chemically etching and removing the first portions of said
resistive layer (72) so as to leave exposed underneath portions of
said dielectric substrate (73); and chemically etching and removing
the first mask.
14. The method of claim 13, wherein chemically etching and
removing, selectively, second portions of said conductive layer
(71) comprises: forming a second mask which, selectively, covers
the third portions of said conductive layer (71) and exposes the
second portions of said conductive layer (71); chemically etching
and removing the second portions of said conductive layer (71) so
as to leave exposed the underneath second portions of said
resistive layer (72); and chemically etching and removing the
second mask.
15. The method of claim 14, wherein forming on the conductive layer
(71) a first mask comprises: applying a first photoresist layer on
the conductive layer (71); selectively exposing portions of said
first photoresist layer to a first UV radiation so as to define
said first mask; and developing said first photoresist layer; and
wherein forming a second mask comprises: applying a second
photoresist layer on the second and the third portions of said
conductive layer (71); selectively exposing portions of said second
photoresist layer to a second UV radiation so as to define said
second mask; and developing said second photoresist layer.
Description
[0001] The present invention relates to an N-way divider/combiner,
with N different from a power of two (N.noteq.2.sup.K, with
K=1,2,3,4, . . . ), obtained in totally planar, monolithic, and
single-face technology. In particular, the present invention finds
advantageous, though non-exclusive, application in distribution
networks for radiofrequency (RF) signals of avionic radars with
electronic beam-scanning antenna.
BACKGROUND OF THE INVENTION
[0002] As is known, in modern radar systems, in particular in
modern avionic radars, the requirements for locating targets and
for security and surveillance have led to the use of electronic
beam-scanning active phased-array antennas.
[0003] In particular, avionic radars based upon electronic
beam-scanning active phased-array antennas comprise, as key
elements, a plurality of transceiver (T/R) modules, each of which
is coupled to a corresponding radiator.
[0004] Furthermore, generally, said radars comprise a distribution
network, which enables, in transmission, distribution of
transmission power to the T/R modules, and, in reception,
combination of the signals received.
[0005] In this regard, schematically illustrated in FIG. 1 is an
example of architecture of an avionic radar 10, which comprises an
electronic beam-scanning active phased-array antenna.
[0006] In particular, the avionic radar 10 comprises a distribution
network, or manifold 11, which in FIG. 1 is indicated as a whole by
a dotted line and comprises, in turn, a port 12 coupled to a
horizontal combiner 13, which is in turn coupled to a plurality of
vertical combiners 14.
[0007] Each vertical combiner 14 is further coupled to a plurality
of T/R modules 15, each of which is coupled to a corresponding
radiator 16.
[0008] In detail, the distribution network 11 enables, in
transmission, propagation of an RF signal from the port 12 to the
T/R modules 15, and, in reception, propagation from the T/R modules
15 to the port 12 of respective RF signals received from the
radiators 16.
[0009] Consequently, as may be readily appreciated, the
distribution network 11 must necessarily comprise one or more
radiofrequency (RF) power dividers/combiners, which will enable:
[0010] in transmission, division of an RF signal present on the
port 12 and having a power equal to P, into a number N of RF
signals, wherein N is the number of T/R modules 15, i.e., of
radiators 16, of the avionic radar 10, each of the N RF signals
having a corresponding power equal to P/N and being inputted, by
the distribution network 11, to a corresponding T/R module 15; and
[0011] in reception, combination of N RF signals received, each,
from a corresponding radiator 16, said combination resulting in an
RF combined signal supplied by the distribution network 11 on the
port 12.
[0012] As is known, radiofrequency (RF) power most widely used
dividers/combiners are Wilkinson dividers/combiners since they
guarantee optimal performance in terms of reduction of transmission
and reflection losses, phase and amplitude matching of the RF
signals at the output ports and insulations between the N channels
into which the input signal is divided.
[0013] In this respect, FIG. 2 illustrates a typical circuit
diagram of a Wilkinson divider/combiner 20 with two ways, i.e.,
with N=2.
[0014] In detail, the Wilkinson divider/combiner 20 comprises:
[0015] a first port P.sub.1, coupled to a first transmission line
21 having a characteristic impedance Z.sub.0; [0016] a second port
P.sub.2, coupled to a first electrical load 22 having an impedance
equal to said characteristic impedance Z.sub.0; [0017] a third port
P.sub.3, coupled to a second electrical load 23 having an impedance
equal to said characteristic impedance Z.sub.0; [0018] a second
transmission line 201, coupled between the first port P.sub.i and
the second port P.sub.2 and having a characteristic impedance equal
to {square root over (2)}Z.sub.0 and an electrical length equal to
.lamda./4, wherein .lamda. is the wavelength corresponding to the
middle frequency of the frequency band of the RF signals for the
propagation of which the Wilkinson divider/combiner 20 is designed;
[0019] a third transmission line 202, coupled between the first
port P.sub.1 and the third port P.sub.3 and having a characteristic
impedance equal to {square root over (2)}Z.sub.0 and an electrical
length equal to .lamda./4; and [0020] a resistance 203 equal to
2Z.sub.0, coupled between the second port P.sub.2 and the third
port P.sub.3 and having the task of uncoupling the second
transmission line 201 and the third transmission line 202 from one
another.
[0021] The Wilkinson divider/combiner 20 enables an ideal power
division to be obtained. In fact, if on the first port P.sub.1 an
RF signal having a power P, is present, then on each of the ports
P.sub.2 and P.sub.3 there will be a corresponding RF signal having
a respective power P.sub.0 equal to P/2.
[0022] In the case wherein an avionic radar with electronic
beam-scanning antenna presents the need for a power
division/combination equal to N=2.sup.K, with K=1,2,3,4, . . . ,
the corresponding manifold of the avionic radar comprises K
Wilkinson dividers/combiners 20 arranged in cascaded fashion,
whereas, when the power division/combination is equal to
N.noteq.2.sup.K, the use of Wilkinson dividers/combiners presents
some problems.
[0023] In this respect, FIG. 3 illustrates a typical circuit
diagram of a Wilkinson divider/combiner 30 with 3 ways, i.e., with
N=3.
[0024] In detail, the Wilkinson divider/combiner 30 comprises:
[0025] a first port P.sub.1, coupled to a first transmission line
31 having a characteristic impedance Z.sub.0; [0026] a second port
P.sub.2, coupled to a first electrical load 32 having an impedance
equal to said characteristic impedance Z.sub.0; [0027] a third port
P.sub.3, coupled to a second electrical load 33 having an impedance
equal to said characteristic impedance Z.sub.0; [0028] a fourth
port P.sub.4, coupled to a third electrical load 34 having an
impedance equal to said characteristic impedance Z.sub.0; [0029] a
second transmission line 301, coupled between the first port
P.sub.i and the second port P.sub.2 and having a characteristic
impedance equal to {square root over (3)}Z.sub.0 and an electrical
length equal to .lamda./4, wherein .lamda. is the wavelength
corresponding to the middle frequency of the frequency band of the
RF signals for the propagation of which the Wilkinson
divider/combiner 30 is designed; [0030] a third transmission line
302, coupled between the first port P.sub.1 and the third port
P.sub.3 and having a characteristic impedance equal to {square root
over (3)}Z.sub.0 and an electrical length equal to .lamda./4;
[0031] a fourth transmission line 303, coupled between the first
port P.sub.1 and the fourth port P.sub.4 and having a
characteristic impedance equal to {square root over (3)}Z.sub.0 and
an electrical length equal to .lamda./4; [0032] a first resistance
304 equal to 3Z.sub.0, coupled between the second port P.sub.2 and
the third port P.sub.3; [0033] a second resistance 305 equal to
3Z.sub.0, coupled between the third port P.sub.3 and the fourth
port P.sub.4; and [0034] a third resistance 306 equal to 3Z.sub.0,
coupled between the second port P.sub.2 and the fourth port
P.sub.4.
[0035] The resistances 304, 305 and 306 have the task of uncoupling
the second transmission line 301, the third transmission line 302,
and the fourth transmission line 303 from one another.
[0036] The Wilkinson divider/combiner 30 enables an ideal power
division to be obtained. In fact, if at the first port P.sub.1 an
RF signal having a power P, is present, then on each of the ports
P.sub.2, P.sub.3 and P.sub.4 there will be a corresponding RF
signal having a respective power P.sub.0 equal to P/3.
[0037] In the case wherein the power division is equal to
N.noteq.2.sup.K with N>3, the Wilkinson topology becomes
complicated considerably in terms of circuit diagram, also on
account of the presence of the uncoupling resistors.
[0038] In avionic radars with electronic beam-scanning antenna, a
fundamental target is the production of N-way, bidirectional, power
dividers/combiners obtained in totally planar, monolithic, and
single-face technology. This derives from the possibility of
"stacking" easily the radiofrequency distribution networks that
join the arrays of radiators.
[0039] Furthermore, said dividers/combiners must present optimal
performance in terms of balancing of amplitude and phase and of
insulations and losses by transmission and reflection.
[0040] In fact, said dividers/combiners must drive the RF signal
towards the T/R modules, and the performance referred to above
considerably affects the radiation pattern.
[0041] When the number of ports to be driven is N=2.sup.K, the
Wilkinson topology described previously proves to be the most
suitable and compliant with the requirements discussed for said
applications.
[0042] When instead, said number of ports is N.noteq.2.sup.K, for
example on account of requirements deriving from considerations
linked to electronic counter-counter measures (ECCMs), the
Wilkinson topology manages to guarantee high levels of electrical
performance, but cannot be developed in planar technology.
[0043] This is caused by the presence of the uncoupling resistors,
which, as may be readily inferred from FIG. 3, cannot be
distributed all in a single plane.
[0044] On the other hand, other topologies of planar power
dividers/combiners have been developed in the course of the years,
but none manages to guarantee the electrical performance of the
Wilkinson topology.
[0045] In fact, the applications in which planar dividers/combiners
are used that have been developed up to now are, for the most part,
aimed at combinations of power amplifiers, for which, unlike
avionic radars with electronic beam-scanning antenna, a slight
degradation of the electrical performance is acceptable.
[0046] Considering the constraint of a planar solution that enables
a compact profile, a reduced weight, and a low cost to be obtained
for the entire avionic radar with electronic beam-scanning antenna,
when the number of ports of the manifold of the avionic radar is
equal to N.noteq.2.sup.K, up to now two solutions have been
possible, both based upon the use of Wilkinson dividers/combiners,
which, as has just been said, are the dividers/combiners that so
far offer the best electrical performance among all the existing
planar dividers/combiners.
[0047] A first solution envisages the use of an M-way Wilkinson
divider/combiner with M=2.sup.L>N, in which each of the
M-N=2.sup.L-N unused output ports is closed on a respective
traditional standard electrical load of 50 .OMEGA..
[0048] For example, if the number N of output ports of the manifold
of the avionic radar with electronic beam-scanning antenna must be
equal to 20, a Wilkinson divider/combiner can be used with M=32
ways, in which each of the M-N=32-20=12 unused output ports is
closed on a respective traditional standard electrical load of 50
.OMEGA..
[0049] Said solution hence presents the marked disadvantage of a
considerable power loss on the matched loads.
[0050] A second solution, instead, is that of using a cascade of
two-way Wilkinson dividers/combiners unbalanced in amplitude and
phase.
[0051] In this respect, FIG. 4 is a schematic illustration of an
example, which is self-explicative for a person skilled in the art,
of a manifold 40 of an avionic radar with electronic beam-scanning
antenna having twenty output ports and comprising a cascade of
two-way Wilkinson dividers/combiners unbalanced in amplitude and
phase.
[0052] From FIG. 4 it may be readily understood how the presence of
different paths for the RF signals that propagate along the
manifold 40 will cause a marked unbalancing in phase and amplitude
on the twenty output ports and consequently a considerable
degradation of the radiation pattern of the radar.
SUMMARY OF THE INVENTION
[0053] The aim of the present invention is hence to provide an
N-way divider/combiner, with N.noteq.2.sup.K, which, in general,
will be able to alleviate the disadvantages just referred to, and
which, in particular, can be obtained in totally planar,
monolithic, and single-face technology and will present excellent
performance in terms of balancing of amplitude and phase and of
insulations and losses by transmission and reflection.
[0054] The aforesaid aim is achieved by the present invention in so
far as it regards an N-way divider/combiner, with N.noteq.2.sup.K,
and a method for the production of an N-way divider/combiner, with
N.noteq.2.sup.K, as defined in the attached claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] For a better understanding of the present invention, some
preferred embodiments, provided purely by way of explanatory and
non-limiting example, will now be illustrated with reference to the
annexed drawings (which are not in scale), wherein:
[0056] FIG. 1 is a schematic illustration of an example of
architecture of an electronic beam-scanning avionic radar;
[0057] FIG. 2 shows a typical circuit diagram of a two-way
Wilkinson divider;
[0058] FIG. 3 shows a typical circuit diagram of a three-way
Wilkinson divider;
[0059] FIG. 4 is a schematic illustration of a manifold of an
avionic radar with electronic beam-scanning antenna having twenty
output ports and comprising a cascade of 2-way Wilkinson dividers
unbalanced in amplitude and phase;
[0060] FIG. 5 shows a circuit diagram of a 3-way power
divider/combiner according to the present invention;
[0061] FIG. 6 shows a circuit diagram of a 5-way power
divider/combiner according to the present invention;
[0062] FIG. 7 shows a cross section of a multilayer structure with
which an N-way power divider/combiner, with N.noteq.2.sup.K,
according to the present invention, may be produced;
[0063] FIG. 8 shows a top plan view of the 3-way power
divider/combiner obtained in totally planar, monolithic, and
single-face technology, the circuit diagram of which is illustrated
in FIG. 5; and
[0064] FIG. 9 shows a top plan view of the 5-way power
divider/combiner obtained in totally planar, monolithic, and
single-face technology, the circuit diagram of which is illustrated
in FIG. 6.
DETAILED DESCRIPTION OF THE DRAWINGS
[0065] The ensuing description is provided to enable a person
skilled in the art to reproduce and use the invention. Various
modifications to the embodiments presented will be immediately
evident to persons skilled in the art, and the generic principles
disclosed herein could be applied to other embodiments and
applications without thereby departing from the scope of the
present invention.
[0066] Hence, the present invention is not to be understood as
limited just to the embodiments described and illustrated, but it
must be granted the widest scope consistently with the principles
and characteristics presented and defined in the annexed
claims.
[0067] The present invention derives from an in-depth study
conducted by the present applicant in order to investigate the
possibility of providing an N-way divider/combiner, with
N.noteq.2.sup.K, in totally planar, monolithic, and single-face
technology that is able to guarantee high levels of electrical
performance at radio frequency. The result of said in-depth study
is the N-way divider/combiner, with N.noteq.2.sup.K, which is
described in what follows.
[0068] In particular, a planar N-way divider/combiner, with
N.noteq.2.sup.K, according to the present invention has a
multi-stage forklike structure, preferably a double-stage forklike
structure, with uncoupling resistances on each stage.
[0069] In detail, provided according to the present invention is an
N-way power divider/combiner, wherein N is an integer different
from a power of two (N.noteq.2.sup.K, with K=1,2,3,4, . . . ),
comprising: [0070] a first port, which is to be coupled to a first
transmission line having a first characteristic impedance; [0071] N
second ports, which are to be coupled each to a corresponding
electrical load, all the electrical loads having one and the same
given load impedance; and [0072] N division/combination branches,
each coupled between the first port and a corresponding second
port.
[0073] Furthermore, the power divider/combiner is configured for:
[0074] dividing a first electrical signal present on the first port
into N second electrical signals; [0075] supplying each of the N
second electrical signals on a corresponding second port; [0076]
combining N third electrical signals present each on a
corresponding second port in a fourth electrical signal; and [0077]
supplying said fourth electrical signal at the first port.
[0078] The power divider/combiner according to the present
invention is characterized: [0079] in that each of the N
division/combination branches comprises a corresponding first
stage, a corresponding second stage, and a corresponding
intermediate node between the corresponding first stage and the
corresponding second stage; and [0080] in that it also comprises,
for each pair of adjacent division/combination branches, a
corresponding first uncoupling resistor coupled between the
corresponding intermediate nodes, and a corresponding second
uncoupling resistor coupled between the corresponding second
ports.
[0081] Preferably, the first electrical signal has a first power
and a first frequency comprised in a given frequency band, and all
the N second electrical signals have the first frequency and one
and the same second power equal to the first power divided by
N.
[0082] Furthermore, all the N third electrical signals have one and
the same third power and one and the same second frequency
comprised in the given frequency band, and the fourth electrical
signal has the second frequency and a fourth power equal to N times
the third power.
[0083] Preferably, all the first uncoupling resistors have one and
the same first electrical resistance, and all the second uncoupling
resistors have one and the same second electrical resistance.
[0084] Furthermore, in each of the N division/combination branches
the corresponding first stage comprises a corresponding second
transmission line coupled between the first port and the
corresponding intermediate node, and the corresponding second stage
comprises a corresponding third transmission line coupled between
the corresponding intermediate node and the corresponding second
port. All the second transmission lines have one and the same
second characteristic impedance and one and the same first
electrical length, and all the third transmission lines has one and
the same third characteristic impedance and one and the same second
electrical length. The first electrical length is an odd integer
multiple of one quarter of a predefined wavelength that corresponds
to a middle frequency of the given frequency band, and the second
electrical length is an odd integer multiple of one quarter of the
predefined wavelength.
[0085] To clarify better the structure of the N-way
divider/combiner, with N.noteq.2.sup.K, according to the present
invention, described by way of example in what follows is a
three-way divider/combiner according to the present invention.
[0086] In particular, illustrated in FIG. 5 is a circuit diagram of
a three-way divider/combiner 50 according to the present
invention.
[0087] In detail, the divider/combiner 50 functions in a frequency
band comprised between 8.5 GHz and 10 GHz and, as illustrated in
FIG. 5, comprises: [0088] a first port P.sub.1, coupled to a first
transmission line 51 having a characteristic impedance Z.sub.0;
[0089] a second port P.sub.2, coupled to a first electrical load 52
having an impedance Z.sub.L; [0090] a third port P.sub.3, coupled
to a second electrical load 53 having the impedance Z.sub.L; [0091]
a fourth port P.sub.4, coupled to a third electrical load 54 having
the impedance Z.sub.L; [0092] a first division/combination branch
501, coupled between the first port P.sub.1 and the second port
P.sub.2; [0093] a second division/combination branch 502, coupled
between the first port P.sub.1 and the third port P.sub.3; and
[0094] a third division/combination branch 503, coupled between the
first port P.sub.1 and the fourth port P.sub.4.
[0095] Furthermore, the first division/combination branch 501 is
divided into a first stage TL.sub.11 and a second stage TL.sub.12
and comprises an intermediate node N.sub.1, the first stage
TL.sub.11 being constituted by a transmission line coupled between
the first port P.sub.1 and the intermediate node N.sub.1 and having
a characteristic impedance equal to Z.sub.1 and an electrical
length equal to .lamda./4 or 3.lamda./4, wherein .lamda. is the
wavelength corresponding to the middle frequency of the frequency
band [8.5 GHz; 10 GHz] of the RF signals for the propagation of
which the divider/combiner 50 has been designed, the second stage
TL.sub.12 being constituted by a transmission line coupled between
the intermediate node N.sub.1 and the second port P.sub.2 and
having a characteristic impedance equal to Z.sub.2 and an
electrical length equal to .lamda./4 or 3.lamda./4.
[0096] Also the second division/combination branch 502 is divided
into a first stage TL.sub.21 and a second stage TL.sub.22 and
comprises an intermediate node N.sub.2, the first stage TL.sub.21
being constituted by a transmission line coupled between the first
port P.sub.1 and the intermediate node N.sub.2 and having the
characteristic impedance Z.sub.1 and an electrical length equal to
.lamda./4 or 3.lamda./4, the second stage TL.sub.22 being
constituted by a transmission line coupled between the intermediate
node N.sub.2 and the third port P.sub.3 and having the
characteristic impedance Z.sub.2 and an electrical length equal to
.lamda./4 or .lamda./4.
[0097] Furthermore, also the third division/combination branch 503
is divided into a first stage TL.sub.31 and a second stage
TL.sub.32 and comprises an intermediate node N.sub.3, the first
stage TL.sub.31 being constituted by a transmission line coupled
between the first port P.sub.1 and the intermediate node N.sub.3
and having the characteristic impedance Z.sub.1 and an electrical
length equal to .lamda./4 or 3.lamda./4, the second stage TL.sub.32
being constituted by a transmission line coupled between the
intermediate node N.sub.3 and the fourth port P.sub.4 and having
the characteristic impedance Z.sub.2 and an electrical length equal
to .lamda./4 or 3.lamda./4.
[0098] Finally, the divider/combiner 50 also comprises: [0099] a
first uncoupling resistor 504, coupled between the intermediate
node N.sub.1 and the intermediate node N.sub.2 and having an
electrical resistance equal to R.sub.1; [0100] a second uncoupling
resistor 505, coupled between the intermediate node N.sub.2 and the
intermediate node N.sub.3 and having the electrical resistance
R.sub.1; [0101] a third uncoupling resistor 506, coupled between
the second port P.sub.2 and the third port P.sub.3 and having an
electrical resistance equal to R.sub.2; and [0102] a fourth
uncoupling resistor 507, coupled between the third port P.sub.3 and
the fourth port P.sub.4 and having the electrical resistance
R.sub.2.
[0103] At this point, in order to characterize completely the
divider/combiner 50 it is necessary to evaluate the four variables
R.sub.1, R.sub.2, Z.sub.1 and Z.sub.2.
[0104] For this purpose it is necessary to set the following
conditions: [0105] the power present on the second port P.sub.2,
the power present on the third port P.sub.3, and the power present
on the fourth port P.sub.4 must all be equal to one another; and
[0106] the sum of the powers present on the second port P.sub.2, on
the third port P.sub.3, and on the fourth port P.sub.4 must be
equal to the power present on the first port P.sub.1.
[0107] Furthermore, considering that on each of the three
division/combination branches 501, 502 and 503 in each of the two
respective stages (TL.sub.11 and TL.sub.12; TL.sub.21 and
TL.sub.22; TL.sub.31 and TL.sub.32) there travels a corresponding
voltage wave equal to
V.sub.ij=V.sub.ij.sup.++V.sub.ij.sup.-
and a corresponding current wave equal to
I.sub.ij=(I.sub.ij.sup.++I.sub.ij.sup.-)Ti.sub.j
with i=1,2,3, which indicates the division/combination branch, and
with j=1,2, which indicates the stage, it is necessary to set the
Kirchhoff laws in the respective nodes across the uncoupling
resistors 504 (N.sub.1 and N.sub.2), 505 (N.sub.2, N.sub.3), 506
(P.sub.2 and P.sub.3), 507 (P.sub.3 and P.sub.4) to guarantee
uncoupling between the division/combination branches 501, 502 and
503. In fact, to obtain a good uncoupling between two
division/combination branches coupled in a node it is sufficient
that in said node the voltage waves of the two division/combination
branches are equivalent.
[0108] Finally, to guarantee a good matching of the ports, in order
to reduce the reflection losses, it is necessary to impose that the
impedance seen by the first port P.sub.1 is equal to Z.sub.0.
[0109] All the aforesaid conditions imposed lead to:
Z.sub.1=(3 Z.sub.0)3/4Z.sub.L.sup.1/4
Z.sub.2=(3 Z.sub.0).sup.1/4Z.sub.L.sup.3/4
R.sub.1=(Z.sub.2.sup.2/Z.sub.L)0.75
R.sub.2=4Z.sub.L
[0110] Illustrated instead in FIG. 6 is a circuit diagram of a
five-way divider/combiner 60 according to the present
invention.
[0111] In detail, the divider/combiner 60 functions in a frequency
band comprised between 8.5 GHz and 10 GHz and, as illustrated in
FIG. 6, comprises: [0112] a first port P.sub.1, coupled to a first
transmission line 61 having a characteristic impedance Z.sub.0;
[0113] a second port P.sub.2, coupled to a first electrical load 62
having an impedance Z.sub.L; [0114] a third port P.sub.3, coupled
to a second electrical load 63 having the impedance Z.sub.L; [0115]
a fourth port P.sub.4, coupled to a third electrical load 64 having
the impedance Z.sub.L; [0116] a fifth port P.sub.5, coupled to a
fourth electrical load 65 having the impedance Z.sub.L; [0117] a
sixth port P.sub.6, coupled to a fifth electrical load 66 having
the impedance Z.sub.L; [0118] a first division/combination branch
601, coupled between the first port P.sub.1 and the second port
P.sub.2; [0119] a second division/combination branch 602, coupled
between the first port P.sub.1 and the third port P.sub.3; [0120] a
third division/combination branch 603, coupled between the first
port P.sub.1 and the fourth port P.sub.4; [0121] a fourth
division/combination branch 604, coupled between the first port
P.sub.1 and the fifth port P.sub.5; and [0122] a fifth
division/combination branch 605, coupled between the first port
P.sub.1 and the sixth port P.sub.6.
[0123] Furthermore, the first division/combination branch 601 is
divided into a first stage TL.sub.11 and a second stage TL.sub.12
and comprises an intermediate node N.sub.1, the first stage
TL.sub.11 being constituted by a transmission line coupled between
the first port P.sub.1 and the intermediate node N.sub.1 and having
a characteristic impedance equal to Z.sub.1, and an electrical
length equal to .lamda./4 or 3.lamda./4, wherein .lamda. is the
wavelength corresponding to the middle frequency of the frequency
band [8.5 GHz; 10 GHz] of the RF signals for the propagation of
which the divider/combiner 60 is designed, the second stage
TL.sub.12 being constituted by a transmission line coupled between
the intermediate node N.sub.1 and the second port P.sub.2 and
having a characteristic impedance equal to Z.sub.2 and an
electrical length equal to .lamda./4 or 3.lamda./4.
[0124] Also the second division/combination branch 602 is divided
into a first stage TL.sub.21 and a second stage TL.sub.22 and
comprises an intermediate node N.sub.2, the first stage TL.sub.21
being constituted by a transmission line coupled between the first
port P.sub.1 and the intermediate node N.sub.2 and having the
characteristic impedance Z.sub.1 and an electrical length equal to
.lamda./4 or 3.lamda./4, the second stage TL.sub.22 being
constituted by a transmission line coupled between the intermediate
node N.sub.2 and the third port P.sub.3 and having the
characteristic impedance Z.sub.2 and an electrical length equal to
.lamda./4 or 3.lamda./4.
[0125] Likewise, also the third division/combination branch 603 is
divided into a first stage TL.sub.31 and a second stage TL.sub.32
and comprises an intermediate node N.sub.3, the first stage
TL.sub.31 being constituted by a transmission line coupled between
the first port P.sub.1 and the intermediate node N.sub.3 and having
the characteristic impedance Z.sub.1 and an electrical length equal
to .lamda./4 or 3.lamda./4, the second stage TL.sub.32 being
constituted by a transmission line coupled between the intermediate
node N.sub.3 and the fourth port P.sub.4 and having the
characteristic impedance Z.sub.2 and an electrical length equal to
.lamda./4 or 3.lamda./4.
[0126] Once again as illustrated in FIG. 6, also the fourth
division/combination branch 604 is divided into a first stage
TL.sub.41 and a second stage TL.sub.42 and comprises an
intermediate node N.sub.4, the first stage TL.sub.41 being
constituted by a transmission line coupled between the first port
P.sub.1 and the intermediate node N.sub.4, and having the
characteristic impedance Z.sub.1 and an electrical length equal to
.lamda./4 or 3.lamda./4, the second stage TL.sub.42 being
constituted by a transmission line coupled between the intermediate
node N.sub.4 and the fifth port P.sub.5, and having the
characteristic impedance Z.sub.2 and an electrical length equal to
.lamda./4 or 3.lamda./4.
[0127] Furthermore, also the fifth division/combination branch 605
is divided into a first stage TL.sub.51 and a second stage
TL.sub.52 and comprises an intermediate node N.sub.5, the first
stage TL.sub.51 being constituted by a transmission line coupled
between the first port P.sub.1 and the intermediate node N.sub.5,
and having the characteristic impedance Z.sub.1 and an electrical
length equal to .lamda./4 or 3.lamda./4, the second stage TL.sub.52
being constituted by a transmission line coupled between the
intermediate node N.sub.5 and the sixth port P.sub.6 and having the
characteristic impedance Z.sub.2 and an electrical length equal to
.lamda./4 or 3.lamda./4.
[0128] Finally, the divider/combiner 60 also comprises: [0129] a
first uncoupling resistor 606, coupled between the intermediate
node N.sub.1 and the intermediate node N.sub.2 and having an
electrical resistance equal to R.sub.1; [0130] a second uncoupling
resistor 607, coupled between the intermediate node N.sub.2 and the
intermediate node N.sub.3 and having the electrical resistance
R.sub.1; [0131] a third uncoupling resistor 608, coupled between
the intermediate node N.sub.3 and the intermediate node N.sub.4 and
having the electrical resistance R.sub.1; [0132] a fourth
uncoupling resistor 609, coupled between the intermediate node
N.sub.4 and the intermediate node N.sub.5 and having the electrical
resistance R.sub.1; [0133] a fifth uncoupling resistor 610, coupled
between the second port P.sub.2 and the third port P.sub.3 and
having an electrical resistance equal to R.sub.2; [0134] a sixth
uncoupling resistor 611, coupled between the third port P.sub.3 and
the fourth port P.sub.4 and having the electrical resistance
R.sub.2; [0135] a seventh uncoupling resistor 612, coupled between
the fourth port P.sub.4 and the fifth port P.sub.5 and having the
electrical resistance R.sub.2; and [0136] an eighth uncoupling
resistor 613, coupled between the fifth port P.sub.5 and the sixth
port P.sub.6 and having the electrical resistance R.sub.2.
[0137] If we set for the divider/combiner 60 conditions similar to
those set for the divider/combiner 50 we obtain
Z.sub.1=(5Z.sub.0).sup.3/4Z.sub.L.sup.1/4
Z.sub.2=(5Z.sub.0).sup.1/4Z.sub.L.sup.3/4
R.sub.1=(Z.sub.2.sup.2/Z.sub.L) 0.4
R.sub.2=3Z.sub.L
[0138] Preferably, both in the divider/combiner 50 and in the
divider/combiner 60, the first stages of the division/coupling
branches have an electrical length equal to 3.lamda./4 rather than
.lamda./4 in order to maintain an appropriate distance between the
different stages TL.sub.ij of the division/combination branches to
prevent undesirable coupling phenomena.
[0139] The aim here is to emphasize how the N-way divider/combiner,
with N.noteq.2.sup.K, according to the present invention will
enable optimal electrical performance in terms of balancing of
amplitude and phase and of insulations and losses by transmission
and reflection, electrical performance that is comparable with that
of Wilkinson dividers/combiners and clearly better, above all for
applications in avionic radars with electronic beam-scanning
antenna, than those of power dividers/combiners belonging to other
known topologies.
[0140] Furthermore, the N-way divider/combiner, with
N.noteq.2.sup.K, according to the present invention can be obtained
in totally planar, monolithic, and single-face technology, unlike
N-way Wilkinson dividers/combiners, with N.noteq.2.sup.K, which,
instead, do not enable a totally planar embodiment on account of
the presence of uncoupling resistors, which cannot be obtained all
in one and the same plane.
[0141] In this regard, described in detail in what follows is a
method for manufacturing the N-way divider/combiner, with
N.noteq.2.sup.K, according to the present invention.
[0142] In particular, the method for manufacturing the N-way power
divider/combiner, with N.noteq.2.sup.K, according to the present
invention comprises: [0143] forming a multilayer structure
comprising a conductive layer, a resistive layer underneath the
conductive layer, and a dielectric substrate underneath the
resistive layer; [0144] chemically etching and removing selectively
first portions of said conductive layer and first portions of said
resistive layer, which are underneath the first portions of said
conductive layer, to form the N division/combination branches; and
[0145] chemically etching and removing selectively second portions
of said conductive layer to form the first and second uncoupling
resistors.
[0146] In what follows, the manufacturing method is described with
explicit reference to organic laminates, it remaining, however,
understood that what will be described can be applied, with the
appropriate variations, for example by replacing the lamination
with a firing process, also on ceramic substrate with a base of
Al.sub.2O.sub.3 (alumina) or AlN (aluminium nitride), both in
thin-film and thick-film configuration.
[0147] Hence, preferably, forming a multilayer structure comprises:
[0148] electrodepositing the resistive layer on the conductive
layer; and [0149] laminating the resistive layer and the conductive
layer on the dielectric substrate.
[0150] In this regard, illustrated in FIG. 7 is a cross section of
a multilayer structure 70 with which the N-way power
divider/combiner, with N.noteq.2.sup.K, according to the present
invention, may be obtained.
[0151] In detail, as illustrated in FIG. 7, the multilayer
structure 70 comprises a conductive layer 71 upon a resistive layer
72, which is in turn set upon a dielectric substrate 73.
[0152] Preferably, the dielectric substrate is a so-called noble
substrate, i.e., one that can be used even in the microwave range,
for example made of PTFE (polytetrafluoroethylene); conveniently,
the substrate Rogers RT6002 having a thickness of 0.635 mm may be
used.
[0153] Conveniently, further, as resistive layer the resistive
layer Omega Ply may be used.
[0154] Preferably, chemically etching and removing selectively
first portions of said conductive layer and first portions of said
resistive layer comprises: [0155] forming on the conductive layer a
first mask which selectively covers the second portions of said
conductive layer and third portions of said conductive layer and
exposes the first portions of said conductive layer, the third
portions of said conductive layer defining the N
division/combination branches, the second portions of said
conductive layer being on top of second portions of said resistive
layer, which define the first and second uncoupling resistors;
[0156] chemically etching and removing the first portions of said
conductive layer so as to leave the underneath first portions of
said resistive layer exposed; [0157] chemically etching and
removing the first portions of said resistive layer so as to leave
underneath portions of said dielectric substrate exposed; and
[0158] chemically etching and removing the first mask.
[0159] Furthermore, preferably, chemically etching and removing
selectively second portions of said conductive layer comprises:
[0160] forming a second mask which selectively covers the third
portions of said conductive layer and exposes the second portions
of said conductive layer; [0161] chemically etching and removing
the second portions of said conductive layer so as to leave the
underneath second portions of said resistive layer exposed; and
[0162] chemically etching and removing the second mask.
[0163] Conveniently, forming a first mask on the conductive layer
comprises: [0164] applying a first photoresist layer on the
conductive layer; [0165] exposing selectively portions of said
first photoresist layer to a first UV radiation in such a way as to
define said first mask; and [0166] developing said first
photoresist layer.
[0167] Furthermore, conveniently, forming a second mask comprises:
[0168] applying a second photoresist layer on the second and third
portions of said conductive layer; [0169] exposing portions of said
second photoresist layer selectively to a second UV radiation in
such a way as to define said second mask; and [0170] developing
said second photoresist layer.
[0171] Finally, illustrated in FIG. 8 and in FIG. 9 are top plan
views, respectively, of the divider/combiner 50 and of the
divider/combiner 60 obtained in totally planar, monolithic, and
single-face technology.
[0172] In particular, in FIGS. 8 and 9 the components of the
divider/combiner 50 and of the divider/combiner 60 are identified
with the same reference numbers used, respectively, in FIG. 5 and
in FIG. 6.
[0173] From the foregoing description the advantages of the present
invention may be readily understood.
[0174] In the first place, the power divider/combiner according to
the present invention enables excellent results to be obtained in
terms of insertion losses, insulation between the output ports,
phase and amplitude balancing and reflection losses, results that
are comparable with those of the Wilkinson divider/combiner.
[0175] Another advantage is linked to the fact that the
divider/combiner according to the present invention is able to
withstand powers in the region of approximately 5 W, said powers
being perfectly congruous with those usually present in
distribution networks for electronic beam-scanning avionic radars
operating at frequencies comprised between 8.5 GHz and 10 GHz.
[0176] Furthermore, unlike N-way Wilkinson dividers/combiners with
N.noteq.2.sup.K, the divider/combiner according to the present
invention can be obtained in totally planar, monolithic, and
single-face technology, and the topology of the divider/combiner
according to the present invention is suited also to its embodiment
in stripline, as well as in microstrip, which increases the
possibilities of application thereof considering that the first
propagation structure increases the packing factor because immunity
to EM (electromagnetic) disturbance is increased.
[0177] On the other hand, the divider/combiner according to the
present invention comprises integrated resistors and consequently
does not require any machining subsequent to the production of the
card itself, such as for example bonding of components, wiring,
etc.
[0178] This enables a considerable reduction in production times
and costs, as well as an increase in terms of reliability and
resistance to the environmental screening of the cards, which are
also more manageable.
[0179] Furthermore, the complete structure is more compact and
requires lower transmission power, and, thanks to the high levels
of electrical performance, also the radiation pattern is more
precise and the overall noise figure of the system is lower.
[0180] A further advantage is linked to the fact that the
divider/combiner according to the present invention enables
distribution networks and hence antenna arrays with an arbitrary
number of radiators to be provided, thus eliminating the constraint
of considering quantities equal to powers of two.
[0181] Finally, it is clear that various modifications may be made
to the present invention, all of which fall within the sphere of
protection of the invention defined in the annexed claims.
* * * * *